KR100356284B1 - Fluorescent lamp with a luminescent material layer thickness adapted to the geometrical discharge distribution - Google Patents

Abstract

A fluorescent lamp, in particular a fluorescent lamp for background lighting of a liquid crystal display screen, having a fluorescent layer thickness change adapted to a change in luminance by a pattern of partial discharges.

Description

Fluorescent lamp with layer thickness of luminescent material suitable for geometric discharge distribution {FLUORESCENT LAMP WITH A LUMINESCENT MATERIAL LAYER THICKNESS ADAPTED TO THE GEOMETRICAL DISCHARGE DISTRIBUTION}

The fluorescent lamp has a gas discharge and a discharge vessel with a fluorescent layer. The electrode structure is designed for dielectric fault discharge. That is, at least part of the electrode is separated from the gas filler by the dielectric. The detailed design of this lamp will be described below only to the extent necessary to understand the present invention.

For the remainder, reference is made to the published prior art below. The contents of the following prior art are incorporated herein.

DE 196 36 965.7 = WO 98/11596

DE 195 26 211.5 = WO / 04625

DE patent 43 11 197.1 = WO 94/23442 DE 198 44 720.4 = WO 00/19485 DE 198 44 721.3 = WO 00/19847 and DE 198 45 228.4 = WO 00/21116

In view of the foregoing, the first prior art discloses an electrode structure, in particular formed by nose-like protruding cathodes, which determines the geometrical distribution of partial discharge during lamp operation.

The present invention relates to fluorescent lamps for dielectrically impeded discharges.

The present invention is based on the technical problem for developing a fluorescent lamp of the type mentioned at the outset such that the luminescence properties are optimized.

According to the invention, this problem is solved by a fluorescent lamp filled with a gas filler and having a discharge tube having a fluorescent layer and an electrode structure for dielectric fault discharge, in which the electrode structure is partially discharged during lamp operation. The geometric distribution of the discharges is determined, and the fluorescent lamps have different layer thicknesses to match the geometric distribution.

The present invention starts with the idea that the uniformity of luminance of the light exit surface is essential for the important possibility of using fluorescent lamps with dielectrically disturbing discharge characteristics. This relates in particular to the design represented by a flat radiator of a fluorescent lamp which essentially consists of a discharge tube consisting of two parallel plates and a frame therebetween. These flat emitters can be used, in particular, for background lighting of display devices mainly liquid crystal display screens. In this case, for example, the luminance variation of 15% is already at the threshold in order not to harm the text readability and the appearance of the display. Meanwhile, the uniformity of luminance plays an important role in other technical fields, and the present invention is not limited to the field of background illumination of flat radiators or display devices.

The distinction between the luminance variation and the allowable luminance variation in the case of compensation by means of the present invention is largely dependent on the conditions of the respective field of use. In particular, when applied to the backlight of a liquid crystal display screen, the luminance reduction in the region between partial discharges should preferably be compensated for at least 20% of the maximum in any case starting from the limit of 15%, 10% or 5%. do.

If the above range of 20% or more with respect to the maximum value is set to the intermediate discharge range, 30% -95% of the maximum layer thickness is improved by the improvement according to the invention in such a way that the discharge in the intermediate discharge area is averaged to the surface thereof. Preferably, a layer thickness reduction of the fluorescent layer of 50% -90% is provided immediately.

In the case of the fluorescent lamp according to the present invention, it is advantageous to spatially fix the individual partial discharges in the total discharge structure for the temporal and spatial stability of the total discharge structure, so the basic concept of the present invention is conventional using the fixing of these partial discharges. The purpose is not to make the fluorescent layer of the fluorescent lamp flat and homogeneous, but rather to design a layer thickness change tailored to the specific geometric distribution of the partial discharges.

For example, the partial discharges fixed by the nose-shaped cathode projections described above are basically triangular when the pulsed active power unit is operated as a first consideration, and is triangular on each cathode projection. To be vertices of and distributed in a predictable manner. The luminance change is then compensated for by the quasi-complementary distribution of the fluorescent material, which occurs in the case of a uniform fluorescent layer thickness based on the partial discharge distribution.

This possibility is due to the inventor's finding that thinning the fluorescent layer in locally defined areas results in a local increase in brightness. The above results are primarily surprising, since it is obvious to assume that the amount of visible light generated is due to the reduction in the amount of fluorescent material. However, since the distribution of visible light in the discharge tube is so scattered that there is no overall direction, the local thinning of the fluorescent layer does not have a noticeable effect on the current intensity of the visible light but rather due to locally reduced absorption and reflection in the fluorescent layer. A significant amount of visible light will be emitted from the fluorescent lamp.

In this case, it is entirely possible to form local cutouts in the fluorescent layer, i.e. reduce the layer thickness to zero, in relation to the layer thickness change or the layer thickness reduction.

Furthermore, the partial discharges are not limited to only partial discharges completely separated from each other. Rather, one can assume a full discharge structure in which partial discharges are the local center of a full discharge structure with multiple centers.

Finally, the present invention is not limited to the particular form of the electrode structure which fixes the arrangement of the partial discharges, or in particular to the above-mentioned cathode projections. In addition to these cathode projections, it is possible to vary the thickness of the electrode dielectric, for example. Thus, in the bipolar operation of the dielectric discharge, all the electrodes are covered with a dielectric layer because the anode and cathode functions of the individual electrodes are alternately replaced. In unipolar operation, at least the anodes are covered with a dielectric layer. On the other hand, to reduce sputter damage on the cathodes, the cathodes are often covered with a thin dielectric layer as well as possible. In each of the above cases, the thickness of each dielectric layer in the spatial surface distribution contributes to the placement of the individual partial discharges. If the layer thickness is thin, the high frequency resistance to the high frequency Fourier components of the individual active power pulses drops, thus raising the electric field effectively present in the gas filler. As a result, the partial discharges form an array of local thin regions of dielectric layers on the electrodes.

Moreover, the electrode width can also be varied. In this case, the partial discharges form an array of locally widened electrode points. This is probably because the larger the locally available electrode surface, the lower the high-frequency resistance and the larger the distribution of shielding counter charges that accumulate on the dielectric surface.

In the thickness change of the fluorescent layer according to the invention, it may be desirable to create an approximately continuous transition between the regions of maximum and maximum layer thicknesses. For this purpose, stepped variations in the layer thickness may be used, for example in transition regions. This is particularly useful in manufacturing methods in which printing methods for phosphor layer deposition are generally used. In the case of the above stepped variations, it is also possible to use two or more partial layers with differing detailed geometries from one another, resulting in the desired stepped variation of the layer thickness during the addition of the partial layers. In this case, manufacture by screen printing is preferable.

However, the entire fluorescent layers produced in the plurality of partial printing steps do not need to be finally stepped. Rather, the production method can be designed such that the partial layers can be deposited at low viscosities or in such a state during drying that they can be present with the steps that originally existed, resulting in a continuous transition.

For effective compensation of the luminance varying with the distribution of the discharge centers, in the projection view, the thinnest angular region of the fluorescent layer is centered between the individual partial discharges in the main light emission direction and the thickest regions are immediately It is preferable to arrange above. In this case, in the case of structures that are fine and can no longer be optically separated outside the lamp, the minimum and maximum layer thicknesses and their regions result in appropriate local averaging.

Placing thin regions of the cutouts or fluorescent layer in the middle between the partial discharges is also advantageous in that the excessively thin fluorescent layer minimizes the loss of ultraviolet light in this region. Consequently, despite the uniform effect of the change in the layer thickness of the fluorescent layer, the total light output of the fluorescent lamp does not change.

As mentioned above, according to the invention the cutouts of the fluorescent layer can also be understood as a change in the layer thickness. Although cutout is another matter, the creation of fluorescent layers with basically uniform layer thicknesses is particularly simple. For example, it can be generated from a single printing step having a suitable structure, such as a printing screen. This is in many cases sufficient for the use of quasi-discrete distributions of layer thickness. Reference is made to exemplary embodiments for this purpose.

In this case, a better transition is made so that the fine pattern of the cutout of the fluorescent layer is (averagely) thin layer thickness region and (averagely) thick by varying the surface ratio of the cutouts and the remaining fluorescent layer in local averaging. A quasi-continuos path can be followed between the layer thickness regions. The term "fine" is measured by the fact that after passing through an external diffuser or milk glass disc, for example, the microstructure of the fluorescent layer can no longer be optically decomposed or separated in the appearance of the fluorescent lamp. As a result, in the case of a fluorescent lamp in which the present invention can be particularly usefully used, since it is possible to optically separate neighboring partial discharges, the structures must be fine compared with the spacing between neighboring partial discharges. To this end, exemplary embodiments are presented.

Another specific geometry of the present invention, as mentioned at the outset, is due to the locally defined nature of the region where the cutouts or phosphor layer thickness is reduced. Such a disproportionately expanded region results in a reduction in the overall yield of the fluorescent lamp due to the significant lack of fluorescent material. Moreover, excessively large areas may appear dark compared to the surrounding area (with fluorescence material), since the emission of diffused light in the discharge tube cannot adequately brighten large areas with excessively small fluorescent layer thicknesses. .

It has been demonstrated that at least for the flat emitter fluorescent lamps described above, the intermediate plate spacing may be an appropriate reference variable. It is preferred that the cutouts are narrower than 100%, preferably 50% or 30% of this interval in at least one direction.

The uniformity of the luminance distribution of the fluorescent lamp of the present invention can in principle also be obtained using known optical diffusers. For the uniformity of luminance as well as the solid angle distribution of the light emission, for example, a material such as a prism foil (a luminance-enhanced foil type of manufacturer 3M), and a scattered foil can be considered. However, the unbalanced use of such an optical diffuser has a fundamental disadvantage in that it reduces the quantity of light combined for the same power. However, the maximization of this amount of light should be prioritized first of all in the case of the already mentioned background lighting. This is a preferred field of use of the present invention.

The compensation effect of the optical diffuser can also be improved by increasing the distance from the flat emitter fluorescent lamp. However, this in many cases increases the overall height which is very limited, especially in the field of backlighting of liquid crystal display screens.

The change in layer thickness, which compensates for the luminance modulation by the partial discharges of the fluorescent lamp, can also be carried out in the same manner as here, combined with appropriate means around the spacer and the support elements. For this purpose, reference is made to the application entitled "Fluorescent lamp having spacers and a locally thinned fluorescent layer thickness" by the same applicant as the present application.

In addition, in this connection, a layer of milk-glass composed of overlay glass on the transparent glass wall defining the discharge tube or composed of the glass wall itself can be used as an optical diffuser.

Some specific and exemplary embodiments of the fluorescent layer structure according to the present invention are presented below. In this case the individual features disclosed may be essential to the invention in combination with others.

1 is a schematic partial view of an electrode structure of a fluorescent lamp according to the invention, wherein the fluorescent lamp has partial discharges between the electrode structures and has a fluorescent layer of a suitable configuration. 2 to 5 each show another example of a fluorescent layer of a suitable configuration, with partial discharges also being shown in part.

1 is a partial view showing a typical electrode structure 2 of a fluorescent lamp according to the present invention, in which the remaining detailed structure of the lamp is omitted for clarity. See prior art for this.

The electrode structure 2 is arranged in a plane on the base plate of the flat emitter fluorescent lamp. Semicircular protrusions 4 facing the anodes near each one are formed on the cathodes. A triangular partial discharge 3 takes place between each of the protrusions 4 and the closest adjacent anode. Thus, the partial discharges 3 are distributed in an essentially flat manner in the flat radiator discharge vessel.

The fluorescent layer 1 essentially corresponding to the white plane of the paper is arranged on this flat arrangement of the partial discharges 3. On the other hand, the fluorescent layer 1 generally includes cutouts 5 whose geometry is consistent with the partial discharges and hatched so as to be distinguished from the partial discharges. These cutouts 5 are arranged between the neighboring partial discharges 3, in particular in a triangle in the opposite direction to the partial discharges. As a result, partial discharges 3 and cutouts 5 are alternately arranged inside each neighboring cathode and anode pair.

If the fluorescent layer 1 configured as above is covered with a frosted-glass plate, attached on the inside of the frosted-glass plate, or an external diffuser is used according to the present invention, The cutouts 5 brighten the intermediate region between the cutouts 5 and the region of the fluorescent layer 1 which appears brighter due to the partial discharges 3 located directly below it, which otherwise looks very dark. You face it. The compensating effect of the frosted glass disk results in a significant reduction in the overall luminance variation.

However, the simple structure disclosed herein further allows each cutout 5 rows alternating on the one hand to abrupt changes between the cutouts 5 and the other adjacent fluorescent layer 1 on the one hand. Between the and partial discharges 3 provides an improvement possibility for strips not covered by the compensation method.

It demonstrates with reference to FIG. The electrodes 2 are not shown in order not to impair the appreciability of the geometric relationship between the cutouts 5 and the partial discharges 3. The difference from the structure shown in FIG. 1 is that the nose-like protrusions 4 (not shown) of the cathode are located at the same height in each case (in the figure), so that the overall pattern of partial discharges is different. Is sorted in a way. The diamond cutouts 5 are thus provided in the relatively large intermediate regions formed between the partial discharges 3. The description mentioned with respect to FIG. 1 is also valid in other refinement examples.

FIG. 3 relates to the electrode structure 2 shown in FIG. 1 and will not be repeated for this reason. However, what has been chosen here is another pattern of cutouts 5 of the fluorescent layer 1 which covers the space between the partial discharges 3 in a slightly different manner. In particular, the empty strip referred to in FIG. 1 is filled here by a linear cutout, and the triangular cutout shown in FIG. 1 extends and joins here to form a serrated line. This structure leads to an improvement in luminance homogeneity compared to FIG. 1, but still shows a sharp change between the cutout 5 and the other continuous fluorescent layer 1.

In contrast, the structure shown in FIG. 4 is slightly different. The geometric basic structure is similar to that of FIG. 3, but linear cutouts and serrated cutouts are fused to form a narrow cutout strip pattern that is placed locally parallel. In detail, the mutual ratio between the width of the cutout strips and the width of the fluorescent layer lying therebetween increases as the distance from the partial discharges 3 increases, and becomes maximum in the middle between the partial discharges.

Averaging with a milk glass disc or other diffuser, these slender structures are no longer visible, as a result of which the layer thickness is effectively approximated in a continuous trend. Therefore, if an appropriate adjustment is made to the nonuniformity of the discharge structure, a wide range of uniformity can be obtained.

The structure shown in FIG. 5 is further advanced in the same direction, in which the strip pattern in FIG. 4 is replaced by an arrangement of fluorescent circles of various diameters (left side of the drawing) surrounded by cutout faces 5. have. The partial discharge triangle 3 is no longer drawn in and lies in the continuous region of the fluorescent layer 1.

The circles were replaced with rectangles of varying corner lengths on the right side of the drawing. Of course, any geometric shape can be assumed, in particular the cutouts 5 can also be located in the peripheral region of the fluorescent material in a circle or square.

Claims (15)

In a fluorescent lamp filled with a gas filler and having a fluorescent layer 1 and a fluorescent lamp having a dielectric failure discharge electrode structure 2, The electrode structure determines the geometric distribution of the partial discharges (3) during operation of the fluorescent lamp, wherein the fluorescent layer (1) has various layer thicknesses adapted to the geometric distribution. The method of claim 1, The electrode structure (2) is characterized in that the geometrical distribution is determined by cathode projections (4). The method according to claim 1 or 2, The electrode structure (2) is characterized in that the geometric distribution is determined by the change in thickness of the electrode dielectric. The method according to claim 1 or 2, The electrode structure (2) is characterized in that the geometric distribution is determined by the change in width of the electrodes. The method according to claim 1 or 2, And the layer thickness change is stepped. The method according to claim 1 or 2, At least for the local average, the layer thickness variation has the thinnest region in the middle between the partial discharges, and has the thickest region just above the partial discharges (3). The method according to claim 1 or 2, The fluorescent lamp, characterized in that the layer thickness change is formed at least in part by the pattern of the cutouts (5) in the fluorescent layer (1). The method of claim 7, wherein Apart from the cutouts (5), the fluorescent lamp (1) is characterized in that it basically has a uniform layer thickness. The method of claim 7, wherein The pattern of cutouts 5 of the fluorescent layer 1, which is fine compared to the spacing between neighboring partial discharges 3, varies between thin and thick regions in the local mean by varying the ratio of cutouts and layer surface. Fluorescent lamp, characterized in that it approaches a quasi-continuous course. The method of claim 7, wherein At least one individual direction cutout (5) is narrower than the distance between two flat plates of the flat emitter discharge tube of the fluorescent lamp. The method according to claim 1 or 2, Fluorescent lamp, characterized in that the layer thickness of the intermediate discharge region with a brightness reduced by at least 20% relative to the maximum is reduced to an average value between 30% and 95% of the layer thickness on the partial discharges (3). The method according to claim 1 or 2, And a milk glass layer at least partially transparent to visible radiation on the wall of the discharge vessel. The method according to claim 1 or 2, The discharge tube is basically formed of two plates arranged in parallel with each other, the electrode structure is disposed on the inner wall of the first plate, and the fluorescent layer is disposed on the inner wall of the second plate. A method of manufacturing the fluorescent lamp according to claim 1 or 2, The fluorescent layer (1) is a method of manufacturing a fluorescent lamp, characterized in that applied to a plurality of partial layers having a geometrical variation by using a printing method. As a method of manufacturing the fluorescent lamp according to claim 13, A method of manufacturing a fluorescent lamp, characterized in that the fluorescent partial layers are screen printed using different screens.